Microdomains in lipid vesicles: structure and distribution assessed by small-angle neutron scattering.

We examined the structure and distribution of microdomains in ternary multilamellar and unilamellar vesicles representing a canonical model raft mixture consisting of dioleoylphosphatidylcholine (DOPC), dipalmitoylphosphatidylcholine (DPPC), and cholesterol via contrast matched small-angle neutron scattering (SANS). The impetus of the work was to reveal the size and distribution of microdomains consistent with the form factor and intermolecular structure factor S(Q) of the scattering pattern of unilamellar and multilamellar vesicles prepared from this ternary lipid system. The data are consistent with the presence of cylindrically shaped microdomains with an average radius of approximately 15 nm assembled in a fractal-like geometry, and with corresponding modeling studies. In the multilamellar vesicle system, coupling of domains across the interlamellar water layer is observed.